Thread rolling die



March 17, 1942. c, c, RICHARDS 2,276,875

veal alga l7 z a l v 2* 5 I M ATToRrW Patented Mar. 17, 1942 THREAD ROLLING DIE I Cecil Charles Richards, West New York, N. J., as-

signor to Groov-Pin Corporation, N. 1., a corporation of New York Application May 3, 1939, Serial No. 271,472

4 Claims.

Among the objects of the present invention are to provide dies for reliably and accurately rolling threads, which dies, however, shall obviate the high cost of machining the same where threads of non-uniform pitch diameter are to be rolled.

Another object is to provide equipment of 'the above type capable of rolling a self-cuttingthread of the type in which cutting grooves traverse the threads and in which the threads and the cutting edges shall nevertheless be reliably produced-sharp and clean throughout;

Among other objects is to provide a method by which an ordinary thread rolling die block of the type for rolling a uniform'thread bolt or stud can be readily modified, without resort to machining operations, so that it may roll a specialized thread as, for instance, one witha reduced pilot end or one with a locking thread and in 'which release of the screw blank from the die after the rolling operation is facilitated.

A feature of the invention is the displacement upward or downward as the case may be, of the material of the die block atportions of its face, in accordance with the contour of screw to be produced. The point forming end of the die for instance is forced upward by driving a wedge into a corresponding slot lengthwise of the die a short distance below the rolling face thereof. At regions where the thread is to be enlarged the faceof the die would be correspondingly forced downward, corresponding transverse slots being provided to admit of such displacement.

Another feature is the conformation of the die to permit the ready release of the rolled screw without deformation of the sharp thread edges thereof. To this end, the material of the die block is transversely slotted from the lower face thereof to near the rolling face thereof and a screw aflixed longitudinally of the block across said slot bends the extremity of the block downward through a range corresponding to the thread height, so that at the release end, there is no further pressure upon the thread being rolled.

Another feature is the conformation of a die complementary to that set forth, to co-act therewith to roll self-cutting screws. This result is accomplished by an insert in the said complementary die at the midsection'thereof, so that the inlet section rolls the threads, the insert rolls the cutting grooves and the outer section of the said complementary die resumes the thread rolling for the purpose of cleaning up any unevenness or burrs produced by the inserted grooving section.

In the accompanying drawing in which are shown one or more of various possible embodiments of the several features of the invention,

Fig. 1 is a perspective of athread rolling die block prior to shaping thereof, showing the assoelated shaping wedges,

Fig. 2 is a transverse sectional view showing the shaping operation,

Fig. 3 is aside elevation of the die with parts in section, v

Fig. 4 is an end elevation of the die on a reduced scale,

Fig. 5 is a plan view of one of various possible die blocks complementary to that of Figs. 1 to 4,

Fig. 6 is a side elevation of the die block of Fig. 5,

Fig. 7 is a fragmentary transverse sectional view, taken on line I of Fig. 5', and

Fig. 8 isJa side elevation of the screw rolled by the particular dies illustratively shown.

Referring now to Figs. 1 to. 4 of the drawing,

' there is shown in Fig. 1 'a die block lllwitha thread rolling face having thread-rolling ribs" -ll thereon. These ribs extend in parallel relation, with their bases in a common plane and with their apices also in a common plane parallel thereto. This obviously is the conventional inexpensive thread rolling face which would serve to rollthreads on a shank of uniform diameter without enlargements, constrictions or tapers or pilots of any kind. v

The die is shown provided with a longitudinal slot I2 extending the entire length of the die block along one side thereof parallel to the rolling face and but a short distance, in the order of inch below-said rolling face. The slot extends into the die material for a distance corresponding to the length of taper to be rolled and is preferably of width in the order of inch.

According to the invention, there is a metal wedge lit with a horizontal lower face l4 and an upper wedge face l5 inclined thereto, desirably at .a wedging angle of 9 to 11 degrees andjoined to the lower face by a rounded end IS. The wedge piece I3 is forced into the slot I! of the die block.

This is preferably done with thedie block at red illustratively shown another arrangement for modifying the die face without machining, and v in this instance, the modification is for the purpose of enlarging the diameter of the threads at the head end of the screw for superior locking effect. To this end, a slot 18 similar to slot I2 is introduced at the right edge of the die and along the length thereof parallel to the rolling face. Slot l8 should be near the die rolling face, nearer than satisfactory for slot l2. Pressure exerted upon the red hot die block will narrow down the slot l8 by depression of the thin tongue of metal III between the thread face and slot it.

Where the enlarged section of screw to be rolled is to remain cylindrical, it may be sufficient ordinarily to deepen the threads at the right end of the die by a further simple machining operation and without resort to slot l8. 'However, where the enlarged end is to have a taper, it is preferable to introduce into the slot IS the wider edge of a steel wedge piece l8, so that in the depression of the face of the die at red heat, against said wedge piece, the said rolling face will slope downward as at [9 to conform to the general inclinationof the wedge piece, which again corresponds to the taper to be imparted to the screw at that region. The wedge piece It remains imprisoned within the die block as shown in Fig. 2.

Referring now to Fig. 3, the die block is shown transversely slotted at near the release end 2| thereof, the said slot extending the entire width of the die and through nearly the entire thickness thereof to near the thread rolling face ll thereof. A screw 22 preferably with a hexagonal head 22' extends longitudinally through the release end of the die block across the slot 20 and is threaded at its point into the body of the die block. The screw thereby causes the slot 20 to be constricted near the lower face of the die block and to correspondingly bend downward the release end of the die block, as shown at 23. The excess material thereby bent below the base of the die block and shown in dash lines at 24 is readily ground off after hardening of the die block as shown in full lines at 25.

Preferably the slot 20 is so proportioned and positioned that the release end of the die becomes bent downward through a range approximately equal to the thread height of the screw to be rolled. Accordingly, if complementary dies are used, one of which is conformed with the transverse slot and bolt as shown in Fig. 3, the thread rolled thereby will be progressively cleared as it is about to be released from the respective dies. The die engages the rolled thread near the end of the rolling operation-to progressively lesser depths, until, at the release extremity of the die, pressure is no longer exerted upon the screw and the latter emerges with its threads clean and sharp cut.

It is understood that the completed die after being formed as set forth, is hardened according to familiar practice, so that in end view it appears as best shown in Fig. 4, with the wedge 13, removed from the now wedge-shaped slot l2, but with the screw 2222' and the wedge piece It permanently in position within the die block.

The slot l2 renders the pilot end forming face of the die block somewhat resilient. This is advantageous in readily accommodating the irregularities commonly occurring in the blank to be rolled, and particularly at the pilot end thereof. While the die block has been shown and described with three separate and distinct specialized formations, one at the left side for the pilot end of the screw to be rolled, one at the right side for the locking head of the screw to be rolled and one at the release end for relieving the screw, and while it is advantageous to use all three of these conformations conjointly for producing a specialized screw, it will be understood that any one of the three modes of formation disclosed, may be used in the absence of either or both of the other two, depending upon the specifications of screws to be rolled.

It will also be understood that the plain machined die block face shown in Fig. 1 may be modified as desired or required to conform the die for any of a wide variety of conformations of screws to be rolled as desired by the use of slots l2 and I8 and wedge pieces I 3 and I8 of corresponding size and shape.

In the rolling of a screw with continuous uninterrupted threads, it will be understood that the die block complementary .to that shown in Figures 1 to 4 would be of substantially conventional construction.

Where a self-cutting screw is to be rolled, the complementary plate might desirably be formed with ribs having a steep rather thana gentlev slope as for instance, according to the teachings of United States Letters Patent No. 2,161,610, issued June 6, 1939, to A. V. Boggild.

In Figs. 5, 6 and 7 there is shown a specialized form of die, complementary to that shown in Figs. 1 to 4, and used therewith for rolling specialized self-cutting screws, such as shown illustratively in Fig. 8. The complementary die plate would have conventional thread rolling ribs 25 extending obliquely thereacross at low pitch corresponding accurately to that of the die shown in Fig. 1. According to the present invention, however, the intermediate section of the die face is modified for a fraction of the width thereof. To this end, the die is notched as at 26 to accommodate an inset piece 21, preferably of the thickness of the die block, which inset piece has throughout the area thereof steep ribs 28 for forming the cutting grooves. The ribs 28 are preferably of height greater than and preferably 10 to 20 per cent higher than the threading ribs 25 as best shown in Fig. 7.

Preferably, the section 29 at the right end of the die of Figs. 5 to 7 has a minimum length of approximately three times the pitch circumference of the screw to be rolled. The insert section 21 at the left of the section 29 and which forms the cutting edges is of length preferably not less than twice the pitch circumference of the screw to be rolled, while the thread cleaning section 30 at the left end of the die should be of length no less than one complete pitch circle of the screw to be rolled.

In use of the dies, it will be apparent that as the right end section 29 of the die is drawn over the blank in passing along the face of the die block I, an uninterrupted thread 2| is rolled. This thread has a reduced pilot end 32 imparted by die portion l1 and an enlarged locking end 32 imparted by die portion [9. As the insert section passed the screw blank, the thread cleaning section 30 engages the screw blank and cleans up construction, and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

l. A thread rolling die having a thread rolling rib along the face thereof, said die being transversely slotted near one end thereof from the under face to near the thread rolling face, said die having a screw extending longitudinally from the end thereof, traversing the thickness of said Accordingly, the screw as shown in slot and threaded into the body of the die and serving to depress the corresponding end portion of the die rolling face.

2. The combination recited in claim 1, in which the slot and holding screw are at the release or leaving end of the die and in which the depression of the die by said releasing end is substantially equal to the thread height of the screw to be rolled thereby.

3. A die for rolling a thread that has a pilot end, said die having thread rolling ribs sloping upward near one lateral edge thereof for forming the pilot end, said die having a slot'longitudinally thereof extending inward at the lateral 'edge from which the pilot is formed to impart resiliency to. the die at said region.

4. A die for rolling a thread that has a pilot end and larger diameter threads near its head, said die having thread rolling ribs sloping upward near one lateral edge thereof for forming the pilot end and with the ribs sloping downward somewhat near the other lateral edge for forming the larger diameter threads, said die having a slot longitudinally thereof extending inward at the lateral edge from which the pilot is formed,

to impart resiliency to the die at said region.

CECIL CHARLES RICHARDS. 

